The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
A continuously variable transmission (“CVT”) typically includes a belt and pulley system that operatively couples a rotary power source, such as an engine or electric motor, to a double gear final drive unit. The belt and pulley system generally includes first and second pairs of pulley cones having a torque transmitting belt or chain extending between the cone pairs. Each pulley cone pair includes an axially stationary pulley member and an axially movable pulley member. Each movable pulley member is axially adjustable with respect to the stationary pulley member by a hydraulic system. The hydraulic system provides primary and secondary hydraulic pressures to the respective movable pulley members to adjust the running radius of the first and second pulley cone pairs which in turn controls the output/input ratio of the continuously variable transmission. Movement of the cones steplessly or continuously varies the ratio of an input speed to an output speed. With the continuously variable transmission, small but effective ratio changes can be attained. This is in contrast to a fixed gear ratio unit where any ratio changes are step values.
A dual clutch transmission (“DCT”) typically includes a pair of mutually exclusively operating input clutches which drive a pair of layshafts or countershafts disposed on opposite sides of an output shaft. One of each of a plurality of pairs of constantly meshing gears which define the various forward gear ratios is freely rotatably disposed on one of the layshafts and the other of each pair of gears is coupled to the output shaft. A plurality of dog clutches or synchronizers selectively couple one of the gears to the layshaft to achieve a forward gear ratio. After the dog clutch is engaged, the input clutch associated with the active layshaft is engaged. Dual clutch transmissions are known for their sporty, performance oriented shift characteristics. They typically exhibit good fuel economy due to good gear mesh efficiency and ratio selection flexibility in design. The dog clutches have low spin losses which also contributes to overall operating efficiency.
Both CVT and DCT transmissions have their advantages, however, there is a need in the art for a dual clutch CVT that has continuously variable operation which is efficient at lower loads and fixed ratio operation which is efficient at relatively higher loads.